The 2017 women's singles champion Garbine Muguruza is the latest big seed to tumble out of Wimbledon at the first round stage.
Muguruza was beaten in straight sets; 6-4, 6-4, by Brazil's Beatriz Haddad Maia.
The 25-year-old Spaniard was seeded number 26 heading into her first match on grass this season and follows up last year's second-round exit with another disappointing early loss.
2004 winner Maria Sharapova retired from the tournament due to a wrist injury while 5-love down in the final set of her first-round match with Pauline Parmentier of France.
It was a better day for the seeds in the women's singles draw starting with the defending champion Angelique Kerber's win; 6-4, 6-3, against Tatjana Maria on Centre Court.
Last year's losing finalist and seven-time champion Serena Williams was made to work for the second set against tenacious Italian Giulia Gatto-Monticone but won; 6-2, 7-5.
Williams is joined in the second round by the top seed Ashleigh Barty who cruised past China's world number 43 ranked Saisai Zheng in straight sets; 6-4, 6-2.
Two-time champion Petra Kvitova, Great Britain's Johanna Konta and American Sloane Stephens were among the other top female seeds to earn routine first-round victories today.
Thiem falls at first Wimbledon hurdle
Dominic Thiem was the big faller at the first hurdle in the men's singles on day two at SW19.
The fifth-seeded Austrian and French Open finalist, currently ranked number four in the world, continued his poor record at Wimbledon with a four set defeat to Sam Querrey; 7-6, 6-7, 3-6, 0-6.
The American has form having taken out the world number one in back-to-back years; Novak Djokovic (2016) and Andy Murray (2017).
It's the second consecutive year that Thiem has bowed out in the first round.
Roger Federer showed some opening round jitters when he lost the first set to South Africa's Lloyd Harris.
But the eight-time men's champion bounced back to win the next three sets on the trot to progress; 3-6, 6-1, 6-2, 6-2.
Kyrgios to meet 'super salty' Nadal in next round at Wimbledon
Two-time winner in 2008 and 2010, Rafael Nadal, is also into the straight second round after he defeated Japanese challenger Yuichi Sugita in three sets; 6-3, 6-1, 6-3.
In round two Nadal will face the man who recently described him as "super salty", the controversial Australian Nick Kyrgios.
"Every time I’ve beaten him ... when he wins, it’s fine," told the No Challenges Remaining podcast. "He won’t say anything bad, he’ll credit the opponent, 'He was a great player'.
"But as soon as I beat him, it’s just like, 'He has no respect for me, my fans and no respect to the game'.
"And I’m like, 'What are you talking about? I literally played this way when I beat you the other previous times and nothing changed...When you beat me in Rome here a couple of years ago, nothing changed; I was the same person'."
Eighth seed Kei Nishikori, Gilles Simon, and Jo-Wilfried Tsonga were just some of the other big names to win their first-round matches this afternoon.
